1. Field of the Invention
The present invention relates to a new method for producing a water-resistant aluminum nitride powder.
2. Description of the Related Art
Aluminum nitride has a good thermal conductivity and electric insulation property. As a method for producing an aluminum nitride powder suitable for a heat radiation filler, Patent Document 1 discloses a method of firing a powder mixture of an alumina or an alumina hydrate, a carbon powder, and a rare earth metal compound at a predetermined temperature in an atmosphere including nitrogen, to progress reductive nitriding of the alumina (or the alumina hydrate).
According to the producing method of Patent Document 1, it is possible to increase the particle size of the aluminum nitride powder to be produced by using the rare earth metal compound (co-melting agent), to thereby obtain an aluminum nitride particle formed in a substantially spherical shape having a size useful as a filler.
On the other hand, aluminum nitride is easily hydrolyzed. Aluminum nitride loses its good property due to generation of aluminum hydroxide by hydrolysis, and a problem on handling, a problem of corrosion and the like occur due to generation of ammonia.
In this regard, in order to add a water-resistant property to the aluminum nitride powder, various methods have been suggested such as phosphorus acid compound treatment of making the aluminum nitride powder contact with a phosphorus acid compound (Patent Documents 2, 3), and silane coupling treatment (Patent Document 4).